Donor Management For Embryo Transfer

The success of any Embryo Transfer programme is based on good stockmanship and attention to detail with respect to general management. Our experience has found the following areas need special attention when preparing donors:

Donor Selection

Young cows (less than 10 years old), with no history of ill health or sub-fertility are the best and most consistent donors, averaging between 5 and 6 embryos per flush. Maiden heifers, older cows (over 10 years old) or those with a poor breeding history, perform more inconsistently, averaging fewer viable embryos.

Pre Programme Preparation

Potential donors should be in a settled management system from four weeks prior to the start of the programme until after the flush has taken place. Cow comfort is important, and whenever possible, the donor should be in a small peer group.

Both "housing" in the autumn and "turn out" in the spring should be anticipated and working at these times should be avoided if possible. If unavoidable, buffer feeding should be used to minimize any detrimental effects.

Routine treatments such as vaccinations, worming, foot trimming or mixing of groups of cattle should also be avoided during the programme.

Donors should be at least 10 weeks calved (for beef breeds) and ideally 12 -14 weeks for heavily lactating dairy cows. They should be clean and cycling (two observed heats are preferred) and a Veterinary check post-calving is recommended. Dairy cows should be past their peak of their lactation with milk solids percentages improving.

Maiden heifers need to be well grown and sexually active before entering an ET programme. The youngest age at which a heifer can be flushed will depend on the breed. On average dairy heifers can be flushed from around 13-14 months, but beef heifers should be slightly older (15-18 months)

Diet and Condition

Animals losing weight are unlikely to respond to superovulation treatment, however obese or "show fit" beef donors, especially maiden heifers, are also unlikely to respond. Donors should be on a rising plane of nutrition, especially with respect to energy. Supplementation with sugar beet pulp for at least four weeks prior to the start of a programme can be beneficial.

Long fibre e.g. hay, big bale silage and straw should be fed to ensure optimum rumen function. Large amounts of concentrate should not be fed at one time (4 kgs maximum). A high protein content in the diet can reduce the number of viable embryos recovered.

Minerals

Experience has shown us that the significance of minerals for optimum performance and fertility remains largely unappreciated in UK herds. It is now apparent that, even when the fertility of a herd is within the accepted range, a significant improvement in ET donor performance will often be seen when extra minerals are supplemented.

Many minerals have a role in reproductive processes including copper, selenium, iodine, zinc, phosphorus and cobalt, and these in particular should be supplemented in ET programmes. Feeding "free access" minerals or reliance on "minerals in the cake" is seldom enough.

Treatment with 1 Ionox and 2 Cosecure boluses prior to starting an ET programme is beneficial. Feeding of a high quality powdered mineral is recommended and mature donors should be fed 150g-200g per day for at least 6 weeks before the planned flush.

Ideally potential donors should be fed the same from calving as this will tend to reduce the calving to first oestrus interval.

Semen Requirements

A minimum of three straws of semen is advisable for each donor. Good semen quality is important for the success of the programme and bulls with below average fertility semen should be avoided.

Increasing the number of straws per insemination (over 2) is seldom likely to increase the number of viable embryos recovered. Extra inseminations during extended estruses is more important.

If there is any doubt on semen quality please discuss it with us. Natural service can be used alone or combined with AI. If using semen from more than one bull, approval from the appropriate breed society is needed.

Disease Status

Diseases which affect general fertility may also affect your ET results. Veterinary advice should be sought on your own herd status.

Diseases to consider should include BVD/Mucosal Disease, IBR and leptospirosis.

Key Points

Ensure settled management before programming

Cows should be at least 10-14 weeks calved and heifers well grown and sexually active before programming

Provide a rising plane of nutrition for 4 weeks prior to superovulation, with particular attention to adequate energy, long fibre, and mineral/trace element supplementation together with moderation of protein intake.

Take care to use good fertility semen

Before programming consult your veterinary surgeon on control of diseases affecting fertility